1. Field of the Invention
The present invention relates to a recording head which records various pieces of information on a magnetic recording medium using a spot light having focused light or a near-field light, a method of manufacturing the recording head, and an information recording and playback apparatus.
2. Background Art
In recent years, there has been demand for a magnetic recording medium (hereinafter, referred to as a disk) such as a hard disk in computer equipment having further high density in response to the need to perform the recording and the playback of mass and high density information, and the like. For this reason, in order to suppress an effect between adjacent magnetic domains or a thermal fluctuation to the minimum, a medium having a strong coercive force has begun to be adopted as the disk. For this reason, it is difficult to record information on the disk.
Thus, in order to solve the disadvantage mentioned above, an information recording and playback apparatus of a hybrid magnetic recording type is provided which locally heats the magnetic domain using the spot light having the focused light or the near-field light having the focused light, temporarily lowers the coercive force, and performs writing onto the disk in the meanwhile.
Particularly, in the case of using the near-field light, it is possible to handle optical information in a region that is equal to or less than the wavelength of light which was limited in an optical system of the related art. Thus, it is possible to promote a high density of a recording bit that surpasses an optical information recording and playback apparatus or the like of the related art.
As a recording head by a hybrid magnetic recording method, various recording heads are provided, but as one of them, a recording head is known which performs the heating using the near-field light (see JP-A-2008-217961).
The recording head described in JP-A-2008-217961 mainly includes a slider, a recording element having a main magnetic pole and a return pole disposed on the slider, a near-field light generating element that generates the near-field light from the irradiated laser light, and an optical waveguide that guides the laser light emitted from a laser light source up to the near-field light generating element.
The near-field light generating element has a core that transmits the laser light while reflecting the same, a light flux transmission element having a cladding that comes into close-contact with the core and seals the core, and a metal film that is disposed between the core and the cladding and generates the near-field light from the laser light. In the core, a cross-section perpendicular to a longitudinal direction (the transmission direction of laser light) facing from one end side to the other end side is formed in a triangular shape, and the core is formed with an aperture so that the cross-sectional area is gradually reduced along the longitudinal direction.
When using the recording head configured in this manner, by generating the near-field light and applying the recording magnetic field, various pieces of information are recorded on the disk. Specifically, in the near-field light generating element, the laser light irradiated from the laser light source is entered from one end side of the core into an inner portion of the core through the optical waveguide. Moreover, the laser light entered to the core is transmitted while being focused from the one end side to the other end side, the laser light is converted to the near-field light by the metal film at the other end side of the core, and the disk is heated by the near-field light. As a consequence, a magnetic recording layer of the disk is locally heated by the near-field light, and the coercive force is temporarily lowered. Furthermore, by supplying the driving current to the recording element simultaneously with the irradiation of the laser light, the recording magnetic field is locally applied to the magnetic recording layer of the disk adjacent to the main magnetic pole.
As a result, it is possible to record various pieces of information on the magnetic recording layer having a temporarily lowered coercive force. That is, the recording onto the disk can be performed by the cooperation of the thermal assist of the near-field light and the magnetic field.
Recently, in the recording head mentioned above, for example, a configuration is being considered in which the laser light source is directly mounted on a slider, and the laser light emitted from the laser light source is directly entered into the core of the near-field light generating element.
However, problems as below are generated when adopting the configuration mentioned above.
That is, as a laser light source mounted on the slider, for example, it is possible to think that a semiconductor laser chip (hereinafter, referred to as a semiconductor laser) of a thin film or the like is used. In this case, since the spot shape of the laser light emitted from the semiconductor laser is a diffusion light of an elliptical shape, in order to make all the laser lights emitted from the semiconductor laser incident into the core, there is a need to increase the size of the cross-sectional area of the incident side end surface of the core.
Meanwhile, in order to promote a reduction in size of the recording head, it is desirable to reduce the cross-sectional area of the core as much as possible. However, in this case, since not all of the laser lights are entered into the core and the loss of the laser light is increased, there is a problem in that a sufficient amount of light cannot be obtained. As a consequence, the generation efficiency of the near-field light is lowered.
Thus, the present invention was made in consideration of such circumstances, and an object thereof is to provide a recording head that can ensure a sufficient amount of light after promoting a reduction in size, a method of manufacturing the recording head, and an information recording and playback apparatus.